5TH NATIONAL CONFERENCE ON THERMOPHYSICAL PROPERTIES: (NCTP‐09)
1249(2010); http://dx.doi.org/10.1063/1.3466563View Description Hide Description
Solid oxide fuel cells (SOFCs) are energy conversion devices that convert chemical energy to electrical energy with high efficiency and have the added advantage of least production of pollutants during their operation. SOFCs comprise of a number of components such as the anode, the electrolyte, the cathode and the interconnect. Each of these components is made of a different material with different thermophysical and electrical properties. Thermal expansion coefficient is one of the most important properties of these compounds. Various components should have matching thermal expansion behaviour to avoid cracking during thermal cycling and for long term operation of SOFCs. In this article, the thermophysical properties of materials for solid oxide fuel cells will be discussed with special emphasize on their thermal expansion behaviour.
1249(2010); http://dx.doi.org/10.1063/1.3466536View Description Hide Description
The present paper reports the investigations on structural relaxation of (9⩽x⩽20) glasses through the study of phase transformation and thermodynamics carried out using differential scanning calorimetry (DSC). The DSC thermograms at constant heating rates exhibit single glass transition and double crystallization on heating, indicating the occurrence of phase separation in these glasses. It has been found through the X‐ray diffraction (XRD) that glasses get crystallized into and PbSe/Se phases after annealing for 2 hrs at an intermediate temperature between first and second crystallization. Kinetics of phase transformation of these glasses studied earliar through the kinetic parameters like activation energy of glass transition and crystallization, avrami exponent, dimensionality of growth show that increase in lead (Pb) contents increases the thermal stability of the glassy samples.
The thermodynamic study made through the determination of parameters like specific heat, entropy difference between metastable states as well as glass and crystalline state, Gibbs free energy difference between glass and crystalline state and enthalpy released during phase transformation (glassy to crystalline) reveals that glass has highest thermal stability among the other samples if the series.
An effort has also been made to study the structural relaxation in the vicinity of glass transition in these glasses. The structural relaxation of ( 18) glassy samples has been studied in terms of excess specific heat and excess enthalpy in the glass transition region. Excess specific heat has been obtained using the specific heat of the as‐prepared sample and that obtained by annealing the sample at two different temperatures below glass transition temperature. The values of excess enthalpy show that glass is more stable than glass, a conclusion which has already been drawn from the study of kinetics of phase transformations and thermodynamics.
1249(2010); http://dx.doi.org/10.1063/1.3466557View Description Hide Description
The present study deals with some results on mechanical and thermal transport properties of PMMA/PC and PMMA/PS polymer blends prepared by solution casting method at concentrations (0, 25, 50, 75, 100 wt%). Dynamic mechanical Analyser (DMA) and Transient Plane Source (TPS) technique have been used to measure the mechanical properties such as Young’s modulus, toughness, tensile strength, elongation at break and the thermal transport properties like thermal conductivity and thermal diffusivity of PMMA/PC and PMMA/PS blends, respectively, at room as well as elevated temperatures. Also the glass transition temperature is determined with the help of DMA of these blended samples. The results show that the mechanical properties of PMMA/PC blends have improved significantly with the increase of PC content in PMMA polymer whereas PMMA/PS blend shows a decreased values of mechanical properties as compared to pure polymers.
The Tan δ result shows a single glass transition for PMMA/PC blend which indicates a good miscibility of the blend, while PMMA/PS blend shows a double glass transition indicating the immiscibility of this blend. Similar behavior has also been exhibited in thermal transport properties. The thermal conductivity of 50PMMA/50PC blend shows an increasing behavior upto the glass transition temperature (130°C) and then decreased with further increase of temperature. In case of immiscible 50PMMA/50PS blend, the values of thermal conductivity shows two maxima corresponding to two glass transition temperatures (88.4 °C and 103.0 °C) obtained. Similar trend has also been observed for thermal diffusivity measurements. For amorphous polymers, phonon can be considered as the chief heat carriers and the observed variation of thermal transport properties with temperature is explained on the basis of structural changes in the samples and mean free path of phonons.
INVESTIGATION OF SOME POTENT MEDICINAL PLANTS OF N.E.INDIA WITH RESPECT TO THERMOPHYSICAL, CHROMATOGRAPHIC AND CRYSTALLOGRAPHIC PROPERTIES1249(2010); http://dx.doi.org/10.1063/1.3466561View Description Hide Description
North East India is readily available of various kinds of medicinal plants. A lot of studies on thermophysical properties of plant leaves, fluids, stems and roots had already been made[3,4,8]. In the present studies of thermophysical properties, chromatographic and crystallographic properties of specific medicinal plant leaves (Azadirechta indica)A, (Vinca rosea)B, (Clerodrendrum colebrookianum)C, (Osimum sanctum)D and fruits (Chisocheton paniculatus) E, and (Cudrania javanensis) F have been made plant based drugs for curing for different chronic diseases.
The thermophysical properties of these leaves and fruits have been studies with XRD, XRF, TG, DTG, DTA, and DSC thermograms. From weight loss(%), time and temperature variations, the Activation Energies of these medicinal plant samples have been computed. The thermal stability is found more for the fruits samples than that of the leave samples.
Thermal behaviours of all six samples have shown hygroscopic behaviour. The results TG, DTG and DTA thermograms confirmed that all samples show similar dehydration and decomposition reactions and hydrophilic nature.
Both chromatographic techniques thin layer (TLC) and Column chromatography have been used for separation of components of the mixtures of samples. From these methods of the fruit sample E a pure crystalline white solids have been identified and confirm them as (MK 01) α‐isomer. Our interest to study the molecular and crystal structure of the sample E.
The single crystal of (MK 01) is found to be orthorhombic cell with lattice parameters with space group
Again from fruit sample F a light yellow solid is isolated and on crystallization give crystalline solid MN‐01 and MN‐02 and it is confirmed that these two compounds are unsaturated isoflavonoids.
The single crystal of MN‐01 has been found monoclinic with lattice parameters and with Space group P‐1.
Again single crystal MN‐02 has been found monoclinic with lattice parameters being with space group
1249(2010); http://dx.doi.org/10.1063/1.3466562View Description Hide Description
1249(2010); http://dx.doi.org/10.1063/1.3466564View Description Hide Description
This work presents formalism for heat capacity at constant volume of linear amorphous and semi‐crystalline polymers, considering both inter‐ and intra‐molecular structural characteristic of these materials. The study reveals that correct identification and estimation of both group and skeletal vibrations is essential for the development of the formalism for of polymers. Further it is shown that for these materials, heat capacity at constant pressure can be obtained through using Nernst‐Lindemann equation. The computed values of and of amorphous PVC and semi‐crystalline poly vinylidene chloride (PVC2) and polychloro‐trifluoro‐ethylene (PCTFE) in the glassy, leathery and rubbery regions i.e around are in excellent agreement with the reported data (maximum deviation 3 % for and values).
1249(2010); http://dx.doi.org/10.1063/1.3466565View Description Hide Description
Polythiophene was chemically synthesized, undoped using aqueous ammonia and then re‐doped using and iodine. Doping concentration was changed by changing the duration of doping process. FTIR results indicate the complex formation between polythiophene and each of the dopants. Elemental analysis results for doped samples show that as the duration increases concentration of ions increases. In case of iodine doped samples atom equivalent of iodine adsorbed per thiophene unit increases with doping duration. TGA analysis shows that doped samples are thermally stable compared to iodine doped samples. Results of differential thermal analysis indicate that Tg values vary with dopant as well as with dopant concentrations. Reduction in Tg values for all the doped samples indicate that acts as plasticizer while increase in Tg values for iodine doped samples indicate antiplasticizer behaviour of iodine in polythophene.
1249(2010); http://dx.doi.org/10.1063/1.3466566View Description Hide Description
Simultaneous measurement of effective thermal conductivity (λ), effective thermal diffusivity (κ) and specific heat of Ker fiber reinforced phenol formaldehyde composites have been studied by transient plane source (TPS) technique. The samples of different weight percentage typically (5, 10, 15, 20 and 25%) have been taken. It is found that values of effective thermal conductivity and effective thermal diffusivity of the composites decrease, as compared to pure phenol formaldehyde, as the fraction of fiber loading increases. Experimental data is fitted on Y. Agari model. Values of thermal conductivity of composites are calculated with two models (Rayleigh, Maxwell and Meredith—Tobias model). Good agreement between theoretical and experimental result has been found.
1249(2010); http://dx.doi.org/10.1063/1.3466567View Description Hide Description
Certain properties of polymers can be enhanced by mixing it with another polymer. When two or more polymers are intimately mixed in a single continuous solid product, the composition is generally referred to as a polymer blend or polyblend. Depending upon the degree of miscibility or immiscibility, such a polyblend may resemble a random copolymer or a block or graft copolymer or it may show micro or macro heterogeneous separation into a multiphase system. Viscosity method is simple and it offers very useful information about the relationship between dilute solution properties and bulk structure of the polymer blend. The basic idea of using viscosity as a parameter for compatibility determination of polymer blends lies in the fact that in solution the repulsive interaction may cause shrinkage of polymer coils resulting in a viscosity of the polymer mixture that is lower than the value calculated from viscosities of the pure components on the assumption of the additive law. In the present study, an attempt has been made to blend PPG 4000 with PEG 4000 in 1,4 ‐Dioxane at 303K at 1% concentration. The blend compositions were formed in the ratio 0:1, 0.2:0.8, 0.4:0.6, 0.5:0.5, 0.6:0.4, 0.8:0.2, 1:0. Relative viscosity of the blend compositions was determined and the values are nonlinear which showed incompatibility. Miscibility nature of the blends were determined further using additive law, log additive law and free volume additive law and the experimental values in all the cases showed negative deviation which is a characteristic of immiscible blend. The miscibility nature of the blend was further confirmed through density, ultrasonic velocity, refractive index and other techniques. The blend showed immiscibility.
Miscibility and Thermophysical Properties of Blend of Poly methyl methacrylate with Polyvinylchloride1249(2010); http://dx.doi.org/10.1063/1.3466568View Description Hide Description
The present paper reports the investigations on miscibility and thermophysical properties of blend of Poly methyl methacrylate with Polyvinylchloride, prepared by solution casting method. The miscibility of the samples is examined by dynamic mechanical analyzer (DMA) and the thermophysical properties (thermal conductivity (λ) and thermal diffusivity (χ)) have been measured using the transient plane source (TPS) technique from room temperature to 100 °C. The results of thermal transport properties of PMMA/PVC blend show an increasing trend of λ and χ upto beyond which they show a decreasing trend. The variation of thermal conductivity and diffusivity of PMMA, PVC and PMMA/PVC blend with temperature is explained on the basis of structural changes of the sample and mean free path of the phonons.
An Investigation of Thermal Characteristic of Mechanical Crimp Textured Polyester Yarn by Differential Scanning Calorimeter (DSC)1249(2010); http://dx.doi.org/10.1063/1.3466569View Description Hide Description
Deficiencies related to the lack of bulk in flat continuous filament yarns make them unsuitable for apparel, home textiles as well as other applications such as car seat covering. Hence, texturising is employed to impart lofty and bulky characteristics to them. The two major texturising techniques employed for polyester yarn are false‐twist and air‐jet texturising. Out of these earlier technique depends on the thermoplasticity of the yarn being textured whereas the later one demands subsequent amount of compressed air to carry out cold fluid texturising. A new concept of mechanical crimp texturising has been designed to overcome these limitations of commercially successful techniques.
In this new technique, pre‐twisted FDY (Fully Drawn Yarn) flat multifilament yarn has been subjected to the higher false‐twisting (depending on yarn fineness) action under the condition of underfeed (depending on ductility of parent yarn). The torque caused due to high level of false‐twisting, forces the filaments to follow helical path at a certain angle (depends on magnitude of twist and denier per filament) to the filament yarn longitudinal axis. Internal stresses arising in single filaments tend to bend the filament and take the shape of spatial helical spring. After the yarn has passed through the false twisting unit, the initial twist would reassert itself and lock the already formed crimpy convolutions in position.
Mechanical crimp textured polyester yarns with different pre‐twist and false‐twist levels have been subjected to thermal stress analysis using differential Scanning Calorimeter (DSC) in heat‐cool‐heat mode. The samples were heated at a rate of 10°C/minute. Almost all samples appear to be crystalline in nature. However, the melting endotherm does not show sharp peak. Instead, the diffuse nature of the peak is a signature of a partial crystalline nature (48%) of the samples. After melting the specimens, cooling of the same leads to crystallization of the material. This is exhibited by the exotherm. Heating the so‐cooled samples, in general, increases their melting point in almost all samples. Thus melting event is shifted towards higher temperature, except for one sample in which pre‐twist level is appreciably high. Thus, DSC is a very useful technique to select and optimize the pre‐twist level and may provide quite a significant insight into the thermal stability of the mechanical crimp textured yarn.
1249(2010); http://dx.doi.org/10.1063/1.3466570View Description Hide Description
Al and Al alloy based ceramic particulate composites have been identified as futuristic materials for a number of engineering applications. The present work reports on synthesis and characterization of reinforced particulate composites with A 384.1 Al alloy as matrix, keeping the particle size constant at 0.220 μm and the composition ( to ). This investigation reveals the effect of reinforcement material and heat treatment i.e. ageing (thermal) on processing and characteristics of these metal matrix composites. The results have been explained in terms microstructural aspects and interfacial characteristics of reinforcement and matrix alloy.
1249(2010); http://dx.doi.org/10.1063/1.3466571View Description Hide Description
The present paper reports the investigation of thermo‐mechanical properties of Poly(methyl methacrylate) or PMMA. The film of PMMA has been prepared by solution casting method taking tetrahydrofuran (THF) as solvent. So prepared film has been used for the measurement of mechanical properties such as storage modulus, loss modulus, Tan δ and stress strain relation employing Dynamic Mechanical Analyzer (DMA). The glass transition temperature of pure PMMA sample has also been obtained in order to determine its physical state and its influence in other properties such as toughness and stiffness. An effort has also been made to study the storage modulus (E’), loss modulus (E”) and Tan δ in a temperature range from 32°C to 140°C by DMA. It has been observed that storage modulus decreases with temperature due to thermal expansion of films. On the other hand Tan δ increases up to glass transition temperature beyond which it shows decreasing trend towards melting. Glass transition temperature is found to be 82.1°C. The stress strain curves of PMMA films at room temperature and at different temperature (32°C–90°C) have been obtained. The results show that the mechanical properties i.e. Young modulus, toughness and tensile strength decrease with increasing temperature whereas the elongation at break shows increasing behavior with temperature. This trend in the different mechanical properties is explained on the basis of free volume theory.
1249(2010); http://dx.doi.org/10.1063/1.3466572View Description Hide Description
Pure and oxalic acid doped conducting polymers (polyaniline and polypyrrole) were chemically synthesized using ammonium persulfate (APS) as an oxidant. These samples were characterized through Scanning Electron Microscopy (SEM), which provides information about the surface topography of polymers. I–V characteristics have been recorded at room temperature as well as in the temperature range from 313 K to 463 K. So obtained characteristic curves were found to be linear. Temperature dependence of conductivity suggests a semiconducting nature in polyaniline samples with increase in temperature, whereas oxalic acid doped polypyrrole sample suggests a transition from semiconducting to metallic nature with the increase of temperature.
1249(2010); http://dx.doi.org/10.1063/1.3466573View Description Hide Description
Thick and thin films of trans‐polyisoprene (TPI) have been prepared using solution casting method by dissolving TPI in toluene. Thick films of TPI have been used to determine thermal transport properties at different temperatures through Thermal Constant Analyzer (TCA). The results show that thermal conductivity, thermal diffusivity and volumetric heat capacity increase with respect to temperature. Thin films of TPI on the other hand have been utilized for the measurement of mechanical properties such as Young’s modulus, tensile strength and toughness. The effect of temperature on the mechanical properties of thin films of TPI has been investigated using Dynamic Mechanical analyzer (DMA) and it was found that the mechanical properties decrease with increasing temperature. Above said behavior of the thermal transport and mechanical properties as a function of temperatures is attributed to the increase in free volume of molecules in chains with temperature.
1249(2010); http://dx.doi.org/10.1063/1.3466574View Description Hide Description
Chalcogenide materials such as CdS/ZnS have been coated on polyethylene terephthalate (PET) films using vacuum thermal evaporation method. Commercial PET film of thickness 20 μm has been used as flexible substrate. The structure of PET and coated materials (CdS, ZnS) has been determined using X‐ray diffraction pattern (XRD). Thermo‐mechanical study of these films has been carried out using Dynamic Mechanical Analyser (DMA). The glass transition temperature of CdS‐PET and ZnS‐PET films have been found to be 118.3°C and 117.4°C respectively whereas of commercial PET film is 89.7°C. The stress‐strain curves of CdS (or ZnS)‐PET films at room temperature explain the mechanical response of these films under the applied load.
1249(2010); http://dx.doi.org/10.1063/1.3466575View Description Hide Description
The water absorptions behaviors of the okra fibers, which are available in north east India, were studied under ambient, annealed, bleached and mercerized conditions by using ordinary gravimetric absorption method. The gains in moisture content in the fibers due to water absorption as well as their capillarity at constant relative humidity were measured as a function of exposure time. In order to ascertain the environment factor of utility of the fibers, the moisture regain of the fibers were determined at different relative air humidity. The water yielding capacity of okra fibers was also determined in order to understand their drying properties. The diffusion coefficients of the sorption process of the fibers under ambient, annealed, bleached and mercerized conditions were estimated.
1249(2010); http://dx.doi.org/10.1063/1.3466576View Description Hide Description
Structural relaxation of isothermally and iscochronally heat treated ( 0.5) glassy alloys have been studied using a differential scanning calorimeter under non‐isothermal conditions. Relaxation enthalpies in the vicinity of glass transition have been recorded on the basis of heat capacity curves of annealed and unannealed samples. Besides relaxation enthalpy, activation energy of structural relaxation for both annealed and unannealed samples have been determined using Kissinger formalism. The results predict that sub‐ annealing of glass leads to decrease in enthalpy of system thereby taking it to more equilibrium configuration. It is also observed that activation energy of structural relaxation is lower for annealed sample than unannealed sample and therefore glass transition occurs at a lower temperature.
1249(2010); http://dx.doi.org/10.1063/1.3466532View Description Hide Description
This paper investigates the particle size distribution, chemical composition, fired modulus of rupture (MOR), and apparent porosity of blended clay utilizing clays available in Bikaner region and comparison with a imported Ukrainian clay. The blended clay B2 presents good white buff fired colour, higher fired modulus of rupture, and low porosity. The blend is suitable for Traditional Indian ceramic industries and a substitute of Ukrainian clay in India.